Joy Slippers

Introduction: Joy Slippers

These slippers work like a joystick, they are designed with two analog sensors on each foot. The sensors measure the pressure being weighted from the body on either the toe-balm or the heal of either foot. Thus enabling Up, Right, Down and Left input to the featured drawing application and games... coming soon.

Later steps in this Instructable will show you how to feed this analog input into your laptop via an Arduino physical computing platform. There are many things that you can do with this input, and I hope to bring out a few interesting applications in the next weeks. This Instructable features a simple drawing application that allows the wearer to control the direction of a line being drawn in real-time and thus draw, using the weight on their feet, in a very simple etch-a-sketch fashion.

The code drawing application code was written in Processing and can be downloaded in STEP 7.

I am also working on developing a simple game application for the input and explore what is possible.

Step 1: Materials and Tools

MATERIALS you will need for the Joy Slippers:
- Conductive thread - 117/17 2ply (www.sparkfun.com)
- Ex-static - plastic from the black bags used to package sensitive electronic components
- 6 mm thick neoprene with jersey on both sides (www.sedochemicals.com)
- 6 metal snaps
- Stretchy fabric (you can also use a pair of old socks if you don't feel like sewing)
- Regular thread

Step 2: Pattern Making and Tracing

Because everybody's feet are different you are going to have to decide who to make these Joy Slippers for.
This Instructable will only go through the steps of creating the left slipper. The right slipper is exactly the same, except you will have to turn the stencils upside down.

Pick a foot, and trace it onto a piece of thin cardboard or thick paper. Before cutting out the tracing draw three petal like shapes on the heel that stick out from your foot. We will call these tabs; they will be where we attach the slippers to the electronics later on.
Cut out the tracing with the tabs. Put your foot back on the tracing and find the areas where 1) your heel presses and 2) the balm of your toes press. In these areas you will want to draw a strips of 1.5cm wide and at the toes: 6cm long and at the heel: 4cm long. Make sure these strips do not come within at least 1cm of the edge. Cut out the insides of these strips and make markings every 1cm along the lengths. In the next step these strips will make sense.

Now you will want to trace these stencils on to the neoprene twice for one foot. Trance one of the tabs on one tracing and the other two along with the other tracing.

Step 3: Sewing Inputs and Vcc

Thread a needle with enough conductive thread. Take the piece of neoprene with only one tab, this is going to be the Vcc, the power supply for the sensor where the 5V from the Arduino will run to. Tie a knot in the end of the thread; do not take the thread double. From the back (in my case black side) poke the needle through the neoprene at one of the end dots of the toe strip marked from the stencil. Stitch back and forth in a diagonal zigzag manor until you reach the other end of the strip. From here go bring the conductive thread back to the back side of the neoprene and make small stitches on the back towards the tab. When you reach the tab, still using the same piece of conductive thread, attach a snap. Thread the needle again and work similar on the heel strip, attaching the end of the conductive thread to the same snap.

Take the other piece of neoprene that has two tabs. Essentially you will do the same here with two exceptions.1) you will connect the pieces of conductive thread to two separate snaps, each on their own tab!2) you will sew the zigzag pattern back-to-front to the way you sewed the Vcc strips! This way, when you lay the pieces of neoprene on top of each other, conductive thread zigzags facing inwards, they will crisscross each other and make for a good connection. I made a thinking mistake here at first and so that is why the stencil is not correct in the first pictures. The close-up picture of the foot stencil is the correct one!

Which side to sew the snaps on? It doesn't really matter if your Vcc or your Inputs go on the top or bottom when you layer them later on. So at the moment it is still undecided which foot you will be able to use this sensitive sole for. When you attach the snaps you will want them all to be facing upwards and this will determine if this is a left or right sole.

Before going onto the next step, now would be a good time to check your connections using a multimeter. Turn the multimeter to measuring the lowest amount of Ohm, or if it has a beet setting, this works best. Now check that each zigzag area of conductive thread is connected to its corresponding snap and ONLY to that one snap and no other! If any of your connections don't work or you accidentally crossed conductive threads and made a wrong connection, you can quite easily just cut off the popper and pull out the conductive thread and start over again.

Step 4: Cutting Ex-static and Sewing Together

Trace the foot stencil onto the ex-static and cut it out about 5mm smaller all-round. You do not need to include the tabs.
Now you will want to layer you pieces as follows so that the snaps are facing upwards:

TOP
- Vcc or Input
- Ex-static
- Input of Vcc
BOTTOM

Now hold everything in place and stitch around the edges of the neoprene. Sewing both layers of neoprene together, better not to include the ex-static in your stitches. Take a good look at the pictures to see how to best stitch it together.

HOW IS THIS GOING TO WORK???
The layers that you have just sewn together create two variable resistors that are pressure sensitive. The layer of ex-static plastic between your conductive thread patches allows for more current to pass through, the harder you push the conductive layers together. I'm not 100% sure why it works, but it does, and it is amazingly stable.

You can now make another multimeter test to make sure none of your Inputs and/or Vcc are touching each other. You should some resistance between the Inputs and the Vcc. And this resistance should become less when you apply pressure to the top of the layers. What you don't want is a permanent connection. Or no connection at all. Or any kind of connection between the Inputs.

Step 5: Finishing the Slipper

Now you will want to maybe improvise and save yourself some cutting and sewing and just attach and old sock to these soles to turn them into wearable slippers. You can also just attach straps of fabric, anything that will hold the sole firmly to the bottom of your feet. If you don'tt want to sew at all, you can try wearing the soles inside some socks or even shoes!

I, myself had a go at designing a slipper pattern, and although it works, it is not optimal. Feel free to copy and alter it. If you decide to sew, you can take the measurements from the picture. I have a size European 39 foot - so make sure to make adjustments for your own size.
Follow the images to get an idea of how to sew the pattern together.

Step 6: Making the Connection to the Arduino

This step shows how to make the connection to the Arduino. For this you will need an Arduino, which is a physical computing platform that has a USB connection to your laptop, contains a microcontroller that we can program to read the variable resistance of the Joy Slippers from its analog inputs.

Of course, if you know what you are doing, you can hook the slippers up to any other circuit or device you have for making use of their variable resistance. So if you don't intend to hook the Joy Slippers up to the Arduino, then you can skip this step.

Because each slipper is individual and depending on all the exact materials that you use and the way you sew them together, the range of variable resistance will be different for each sensor (right toe, right heel, left toe, left heel). This is why there is a threshold function in the processing applet.

**EASY THRESHOLDING NOW IMPLEMENTED**

There is a threshold function in the processing applet that allows you to set the MIN and MAX values of your sensor. These will be between 0 and 1023.

To find out what these thresholds are and to switch to the drawing function you will need to read the instructions in the code and follow them.

MIN threshold should be slightly above resting state and MAX threshold should be maximum value obtained when pushing as hard as possible on the Joy Slippers.

I'm currently developing different applications, also games for the Joy Slipper. I am also working on improving the slippers and would appreciate any feedback you can give me after having read though this Instructable.